Are Antibacterial Soaps Really Better?

Citing new data about the potential health risks associated with the active ingredients in most antibacterial soaps, the Food and Drug Administration announced this week that it is asking soap manufacturers to prove that the benefits of antibacterial soaps outweigh the risks—or take them off the market. The new proposal comes in light of recent data suggesting that the active ingredients in most antibacterial soaps, triclosan (in liquid soaps) or triclocarban (in bar soaps), may affect hormonal systems, according to animal studies, coupled with new evidence that humans may be exposed to much higher levels of these drugs over a lifetime than researchers previously believed.

"Antibacterial soaps are used extensively by millions of consumers, and people may be exposed to these products repeatedly, on a daily basis over the course of their lifetime," FDA spokeswoman Andrea Fischer told PopMech via email. "Because of this extensive exposure, we believe that any potential risk from the use of an antibacterial soap should be balanced with a clearly demonstrated benefit."

How It Works

Triclosan and triclocarban are chlorinated hydrocarbons that can kill many bacteria and some fungi. Three-quarters of national-brand liquid soaps and about one-third of bar soaps contain them, according to a 2001 study. They are also found in other products, including toothpaste, mouthwash, and toys. Triclosan stymies bacteria by interfering with a protein that they need to generate new lipids and build their cell walls, says Stuart B. Levy, director of the Center for Adaptation Genetics and Drug Resistance at Tufts University School of Medicine and cofounder of the Alliance for the Prudent Use of Antibiotics. Levy's lab figured out triclosan's bacteria-killing mechanism.

"The bacteria can begin to grow, but if they don't have a cell wall, they will lyse, that is, break the cells," he says. "The cells are dead."

By contrast, regular soap mechanically removes bacteria but doesn't necessarily kill them, Levy says. "We use regular soap to get bacteria off our skin, off our hands, off our face. It dislodges that adherence they have to the skin of individuals, and they just wash it down the drain. That's why we say that soap and water are really the first line of attack against infections of the skin."

Are They More Effective?

The question is, are antibacterial soaps actually better than ordinary soap and water at preventing illness? No, FDA lead microbiologist Colleen Rogers says in a press release. And she says the FDA will seek more information from soap manufacturers to prove antibiotic products really are better.

To that point, the FDA is proposing to change the way it defines effectiveness. Previously, the effectiveness of an antimicrobial soap was defined by the number of bacteria it removed from the skin. Soap manufacturers have hyped their products by claiming that antibacterial soaps get rid of more skin bacteria than regular soaps do: In a statement responding to the FDA proposal, the American Cleaning Institute—a trade organization representing manufacturers of soap and other cleaning products—reiterated that argument by citing a meta-analysis (which they and another trade organization funded) that backed up that claim. The FDA, however, says that only one study sufficiently demonstrated that antibacterial soap eliminated more bacteria than a control soap.

And even if triclosan does reduce levels of skin bacteria, it's unknown how that relates to incidence of infection, the FDA says. So in the current proposal, the FDA is requiring soap manufacturers to present data from clinical trials proving that antibacterial soaps reduce infection better than regular soap.

According to the FDA report, there have been two well-designed studies to test the effects of antibacterial soap on incidence of illness. One of these, a 2005 study published in The Lancet, compared illness in three Pakistani squatter neighborhoods in which people were given and encouraged to use either triclocarban-containing soap, regular soap, or no soap at all. While the study found that using soap of either kind reduced childhood instances of diarrhea, respiratory infections, and skin infections, it did not demonstrate any benefit from the antibacterial soap over regular soap. The other study that the FDA cited, which took place in urban U.S. neighborhoods, also failed to show a benefit for antibacterial soap.

"None of studies published to date have persuaded me that there is a health benefit to including antibacterial compounds in soap," says Stephen Luby, professor of medicine at Stanford University, who led the study in Pakistan.

Safety Concerns

The FDA isn't so sure about the safety of antibacterial soaps, either. According to its new proposal, studies suggest that "triclosan and triclocarban can cause alterations in thyroid, reproductive, growth, and developmental systems of neonatal and adolescent animals." While one should not assume the results would be the same in humans, researchers interpret the animal studies as flagging this chemical as a potential risk. Noting changes in sexual development that some animal studies associated with triclosan exposure, Levy says, "We don't say [the same thing] happens in people, we don't say it will, we just say be careful, because it may well be an indicator of a toxicity that we should be concerned about."

The FDA wants to be extra careful because these chemicals are everywhere. In the last decade, the agency says, new studies have shown that humans have greater exposure to triclosan, which is absorbed through the skin, than was previously known. With a large enough exposure, even a mildly toxic chemical could be harmful. Three-quarters of Americans had triclosan in their urine in 2003–2004, according to the National Health and Nutrition Examination Survey, a CDC-run study. Studies have also found triclosan in breast milk.

Furthermore, the FDA is concerned that triclosan could contribute to antibiotic resistance. In the lab, Levy and others have shown that triclosan selects for bacteria in which a normally inactive pump for removing drugs from cells is turned on. The pump, activated through mutation, makes the cells triclosan-resistant by pumping triclosan out of the cell. It also makes bacteria resistant to other antibiotics that are important for controlling infections. Though antibiotic resistance is a growing concern, the data about triclosan and antibiotic resistance "are not sufficient to conclude that the use of triclosan poses a public health risk," concluded European review committees mentioned in the FDA report.

The Consequences

Following a 180-day comment period, soap manufacturers have one year to provide the new data the FDA has requested, with the possibility of a time extension. If manufacturers fail to show that the health benefits of these soaps outweigh their risks, they will have to either remove the antibacterial drug from their soaps or remove the antibacterial claim from the label.

"I don't think that there is a huge negative effect associated with these compounds," Luby says. "On the other hand, since we have been unable to demonstrate any positive effects, I don't see any reason why we as a society should bear the risk, and so I think the FDA's position is reasonable and aligned with the public interest."

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